Kira Beltran | 3 months ago
Technical Content

Sweet And Sour Crude Oil: H2S, Corrosion, and Material Selection

Crude oil is a naturally occurring type of fossil fuel refined to produce usable products. It's located underground and extracted through drilling. There are over 160 different crude oils traded on the market today. These oils are typically labeled by the region, and have a specific chemical makeup. The chemical makeup defines the quality characteristics which impact the market value of individual crude streams.

Sweet and Sour Crude

Sulfur content determines the sweetness of an oil stream. Crude oil with low sulfur content below 0.5% is classified as "sweet" while anything above 0.5% is regarded as “sour.” Brent and WTI are the more familiar sweet crudes in the market and continue to dominate the global benchmark pricing.
Sour crude is known for its high sulfur content which leads to high quantities of hydrogen sulfide (H2S) that can pose serious health problems or even be fatal. Due to the risks involved, sour crude has to be stabilized through the removal of H2S before it can be transported and refined. Some of the sourest crude can be found in Mexico, Venezuela, and Canada while the Gulf of Mexico and a number of the OPEC Middle East countries also produce high volumes of sour crude.

Sour Crude and Corrosion Risks

Sour crudes contain considerable quantities of H2S, CO2, and salted formation waters that comprise high corrosivity properties and are flammable and toxic. The corrosive conditions can push alloys to their limits and contribute to sulfide stress cracking (SSC) in higher-strength carbon steel and low-alloy steel. SSC can lead to the partial or complete loss of a material's ductility, making it brittle, and cause sudden failure of normally pliable metal alloys. Any leaks that occur due to corrosion can be costly and have disastrous consequences on safety and the environment. (2)

Material Matters

When producing sour crude in these challenging environments, corrosion resistant alloys are often used for the production tubulars and completion equipment in order to significantly reduce the risk of SSC and SCC as well as extending the life of the well. NACE MR0175/ISO 15156 serves as the industry guideline for selection of materials for sour service.
PipeSearch provides high quality, corrosion resistant alloy tubulars and gives its customers confidence in the material quality. When it comes to alloy confirmation, we not only verify, we validate. We combine visual verification techniques with positive material identification (PMI) readings. The PMI reads the product chemistry and validates the alloy in the review. Our commitment to quality and reliability is what differentiates us. We connect critical projects with the materials that are vital to the drilling operations. Please click here to view our full product guide.


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